In general, OCI applications do not work with internal data type representations of data, but with host language data types that are predefined by the language in which they are written. When data is transferred between an OCI client application and a database table, the OCI libraries convert the data between internal data types and external data types.

External data types are host language types that have been defined in the OCI header files. When an OCI application binds input variables, one of the bind parameters is an indication of the external data type code (or SQLT code) of the variable. Similarly, when output variables are specified in a define call, the external representation of the retrieved data must be specified.

In some cases, external data types are similar to internal types. External types provide a convenience for the programmer by making it possible to work with host language types instead of proprietary data formats.

Note:

Even though some external types are similar to internal types, an OCI application never binds to internal data types. They are discussed here because it can be useful to understand how internal types can map to external types.

OCI can perform a wide range of data type conversions when transferring data between an Oracle database and an OCI application. There are more OCI external data types than Oracle internal data types. In some cases, a single external type maps to an internal type; in other cases, multiple external types map to a single internal type.

The many-to-one mappings for some data types provide flexibility for the OCI programmer. For example, suppose that you are processing the following SQL statement:

SELECT sal FROM emp WHERE empno = :employee_number

You want the salary to be returned as character data, instead of a binary floating-point format. Therefore, you specify an Oracle database external string data type, such as VARCHAR2 (code = 1) or CHAR (code = 96) for the dty parameter in the OCIDefineByPos() or OCIDefineByPos2() call for the sal column. You also must declare a string variable in your program and specify its address in the valuep parameter. See Table 3-2 for more information.

If you want the salary information to be returned as a binary floating-point value, however, specify the FLOAT (code = 4) external data type. You also must define a variable of the appropriate type for the valuep parameter.

Oracle Database performs most data conversions transparently. The ability to specify almost any external data type provides a lot of power for performing specialized tasks. For example, you can input and output DATE values in pure binary format, with no character conversion involved, by using the DATE external data type.

To control data conversion, you must use the appropriate external data type codes in the bind and define routines. You must tell Oracle Database where the input or output variables are in your OCI program and their data types and lengths.

OCI also supports an additional set of OCI typecodes that are used by the Oracle Database type management system to represent data types of object type attributes. You can use a set of predefined constants to represent these typecodes. The constants each contain the prefix OCI_TYPECODE.

In summary, the OCI programmer must be aware of the following different data types or data representations:

Internal Oracle data types, which are used by table columns in an Oracle database. These also include data types used by PL/SQL that are not used by Oracle Database columns (for example, indexed table, boolean, record).

External OCI data types, which are used to specify host language representations of Oracle data.

OCI_TYPECODE values, which are used by Oracle Database to represent type information for object type attributes.

Information about a column's internal data type is conveyed to your application in the form of an internal data type code. With this information about what type of data is to be returned, your application can determine how to convert and format the output data. The Oracle internal data type codes are listed in the section Internal Data Types.

About Using External Data Type Codes

An external data type code indicates to Oracle Database how a host variable represents data in your program. This determines how the data is converted when it is returned to output variables in your program, or how it is converted from input (bind) variables to Oracle Database column values. For example, to convert a NUMBER in an Oracle database column to a variable-length character array, you specify the VARCHAR2 external data type code in the OCIDefineByPos() call that defines the output variable.

To convert a bind variable to a value in an Oracle Database column, specify the external data type code that corresponds to the type of the bind variable. For example, to input a character string such as 02-FEB-65 to a DATE column, specify the data type as a character string and set the length parameter to 9.

It is always the programmer's responsibility to ensure that values are convertible. If you try to insert the string "MY BIRTHDAY" into a DATE column, you get an error when you execute the statement.

See Also:

Table 3-2 for a complete list of the external data types and data type codes

Internal Data Types

Lists and describes the internal data types.

Table 3-1 lists the internal Oracle Database data types (also known as built-in), along with each type's maximum internal length and data type code. PL/SQL types listed in Table 3-10 and Table 3-11 are also considered to be internal data types.

Character Strings and Byte Arrays

Use Oracle internal data types to specify columns that contain characters or arrays of bytes.

You can use following Oracle internal data types to specify columns that contain characters or arrays of bytes: CHAR, VARCHAR2, RAW, LONG, and LONGRAW.

Note:

LOBs can contain characters and BFILEs can contain binary data. They are handled differently than other types, so they are not included in this discussion.

CHAR, VARCHAR2, and LONG columns normally hold character data. RAW and LONGRAW hold bytes that are not interpreted as characters (for example, pixel values in a bit-mapped graphic image). Character data can be transformed when it is passed through a gateway between networks. Character data passed between machines using different languages, where single characters may be represented by differing numbers of bytes, can be significantly changed in length. Raw data is never converted in this way.

It is the responsibility of the database designer to choose the appropriate Oracle internal data type for each column in the table. The OCI programmer must be aware of the many possible ways that character and byte-array data can be represented and converted between variables in the OCI program and Oracle Database tables.

When an array holds characters, the length parameter for the array in an OCI call is always passed in and returned in bytes, not characters.

UROWID

The Universal ROWID (UROWID) is a data type that can store both logical and physical rowids of Oracle Database tables. Logical rowids are primary key-based logical identifiers for the rows of index-organized tables (IOTs).

To use columns of the UROWID data type, the value of the COMPATIBLE initialization parameter must be set to 8.1 or later.

The following host variables can be bound to Universal ROWIDs:

SQLT_CHR (VARCHAR2)

SQLT_VCS (VARCHAR)

SQLT_STR (NULL-terminated string)

SQLT_LVC (LONG VARCHAR)

SQLT_AFC (CHAR)

SQLT_AVC (CHARZ)

SQLT_VST (OCI String)

SQLT_RDD (ROWID descriptor)

BINARY_FLOAT and BINARY_DOUBLE

The BINARY_FLOAT and BINARY_DOUBLE data types represent single-precision and double-precision floating point values that mostly conform to the IEEE754 Standard for Floating-Point Arithmetic.

Prior to the addition of these data types with release 10.1, all numeric values in an Oracle Database were stored in the Oracle NUMBER format. These new binary floating point types do not replace Oracle NUMBER. Rather, they are alternatives to Oracle NUMBER that provide the advantage of using less disk storage.

These internal types are represented by the following codes:

SQLT_IBFLOAT for BINARY_FLOAT

SQLT_IBDOUBLE for BINARY_DOUBLE

All the following host variables can be bound to BINARY_FLOAT and BINARY_DOUBLE data types:

SQLT_BFLOAT (native float)

SQLT_BDOUBLE (native double)

SQLT_INT (integer)

SQLT_FLT (float)

SQLT_NUM (Oracle NUMBER)

SQLT_UIN (unsigned)

SQLT_VNU (VARNUM)

SQLT_CHR (VARCHAR2)

SQLT_VCS (VARCHAR)

SQLT_STR (NULL-terminated String)

SQLT_LVC (LONGVARCHAR)

SQLT_AFC (CHAR)

SQLT_AVC (CHARZ)

SQLT_VST (OCIString)

For best performance, use external types SQLT_BFLOAT and SQLT_BDOUBLE in conjunction with the BINARY_FLOAT and BINARY_DOUBLE data types.

External Data Types

Lists and describes the data type codes for external data types.

Table 3-2 lists data type codes for external data types. For each data type, the table lists the program variable types for C from or to which Oracle Database internal data is normally converted.

VARCHAR2

The VARCHAR2 data type is a variable-length string of characters with a maximum length of 4000 bytes. If the init.ora parameter max_string_size = standard (default value), the maximum length of a VARCHAR2 can be 4000 bytes. If the init.ora parameter max_string_size = extended, the maximum length of a VARCHAR2 can be 32767 bytes.

Note:

If you are using Oracle Database objects, you can work with a special OCIString external data type using a set of predefined OCI functions. See Object-Relational Data Types in OCI for more information about this data type.

If the value_sz parameter is greater than zero, Oracle Database obtains the bind variable value by reading exactly that many bytes, starting at the buffer address in your program. Trailing blanks are stripped, and the resulting value is used in the SQL statement or PL/SQL block. If, with an INSERT statement, the resulting value is longer than the defined length of the database column, the INSERT fails, and an error is returned.

Note:

A trailing NULL is not stripped. Variables should be blank-padded but not NULL-terminated.

If the value_sz parameter is zero, Oracle Database treats the bind variable as a NULL, regardless of its actual content. Of course, a NULL must be allowed for the bind variable value in the SQL statement. If you try to insert a NULL into a column that has a NOTNULL integrity constraint, Oracle Database issues an error, and the row is not inserted.

When the Oracle internal (column) data type is NUMBER, input from a character string that contains the character representation of a number is legal. Input character strings are converted to internal numeric format. If the VARCHAR2 string contains an illegal conversion character, Oracle Database returns an error and the value is not inserted into the database.

Output

You must specify the desired length for the return value in value_sz for bind and define functions.

Specify the desired length for the return value in the value_sz parameter of the OCIDefineByPos() call, or the value_sz parameter of OCIBindByName() or OCIBindByPos() for PL/SQL blocks. If zero is specified for the length, no data is returned. If you are using extended VARCHAR2 lengths, then the value_sz parameter determines the desired length for the return value in the OCIDefineByPos2() call, or in the OCIBindByName2() and OCIBindByPos2() calls for PL/SQL blocks.

If you omit the rlenp parameter of OCIDefineByPos(), returned values are blank-padded to the buffer length, and NULLs are returned as a string of blank characters. If rlenp is included, returned values are not blank-padded. Instead, their actual lengths are returned in the rlenp parameter.

To check if a NULL is returned or if character truncation has occurred, include an indicator parameter in the OCIDefineByPos() call. Oracle Database sets the indicator parameter to -1 when a NULL is fetched and to the original column length when the returned value is truncated. Otherwise, it is set to zero. If you do not specify an indicator parameter and a NULL is selected, the fetch call returns the error code OCI_SUCCESS_WITH_INFO. Retrieving diagnostic information for the error returns ORA-1405.

NUMBER

You should not need to use NUMBER as an external data type.

If you do use it as an external data type, Oracle Database returns numeric values in its internal 21-byte binary format and expects this format on input. The following discussion is included for completeness only.

Note:

If you are using objects in an Oracle database, you can work with a special OCINumber data type using a set of predefined OCI functions.

Oracle Database stores values of the NUMBER data type in a variable-length format. The first byte is the exponent and is followed by 1 to 20 mantissa bytes. The high-order bit of the exponent byte is the sign bit; it is set for positive numbers, and it is cleared for negative numbers. The lower 7 bits represent the exponent, which is a base-100 digit with an offset of 65.

To calculate the decimal exponent, add 65 to the base-100 exponent and add another 128 if the number is positive. If the number is negative, you do the same, but subsequently the bits are inverted. For example, -5 has a base-100 exponent = 62 (0x3e). The decimal exponent is thus (~0x3e) -128 - 65 = 0xc1 -128 -65 = 193 -128 -65 = 0.

Each mantissa byte is a base-100 digit, in the range 1..100. For positive numbers, the digit has 1 added to it. So, the mantissa digit for the value 5 is 6. For negative numbers, instead of adding 1, the digit is subtracted from 101. So, the mantissa digit for the number -5 is 96 (101 - 5). Negative numbers have a byte containing 102 appended to the data bytes. However, negative numbers that have 20 mantissa bytes do not have the trailing 102 byte. Because the mantissa digits are stored in base 100, each byte can represent 2 decimal digits. The mantissa is normalized; leading zeros are not stored.

Up to 20 data bytes can represent the mantissa. However, only 19 are guaranteed to be accurate. The 19 data bytes, each representing a base-100 digit, yield a maximum precision of 38 digits for an Oracle NUMBER.

If you specify the data type code 2 in the dty parameter of an OCIDefineByPos() or OCIDefineByPos2() call, your program receives numeric data in this Oracle internal format. The output variable should be a 21-byte array to accommodate the largest possible number. Note that only the bytes that represent the number are returned. There is no blank padding or NULL termination. If you must know the number of bytes returned, use the VARNUM external data type instead of NUMBER.

64-Bit Integer Host Data Type

You can bind and define integer values greater than 32-bit size (more than nine digits of precision) from and into a NUMBER column using a 64-bit native host variable and SQLT_INT or SQLT_UIN as the external data type in an OCI application.

Starting with release 11.2, OCI supports the ability to bind and define integer values greater than 32-bit size (more than nine digits of precision) from and into a NUMBER column using a 64-bit native host variable and SQLT_INT or SQLT_UIN as the external data type in an OCI application.

This feature enables an application to bind and define 8-byte native host variables using SQLT_INT or SQLT_UIN external data types in the OCI bind and define function calls on all platforms. The OCIDefineByPos() or OCIDefineByPos2(), OCIBindByName() or OCIBindByName2(), and OCIBindByPos() or OCIBindByPos2() function calls can specify an 8-byte integer data type pointer as the valuep parameter. This feature enables you to insert and fetch large integer values (up to 18 decimal digits of precision) directly into and from native host variables and to perform free arithmetic on them.

INTEGER

The INTEGER data type converts numbers. An external integer is a signed binary number; the size in bytes is system-dependent. The host system architecture determines the order of the bytes in the variable. A length specification is required for input and output. If the number being returned from Oracle Database is not an integer, the fractional part is discarded, and no error or other indication is returned. If the number to be returned exceeds the capacity of a signed integer for the system, Oracle Database returns an "overflow on conversion" error.

FLOAT

The FLOAT data type processes numbers that have fractional parts or that exceed the capacity of an integer. The number is represented in the host system's floating-point format. Normally the length is either 4 or 8 bytes. The length specification is required for both input and output.

The internal format of an Oracle number is decimal, and most floating-point implementations are binary; therefore, Oracle Database can represent numbers with greater precision than floating-point representations.

Note:

You may receive a round-off error when converting between FLOAT and NUMBER. Using a FLOAT as a bind variable in a query may return an ORA-1403 error. You can avoid this situation by converting the FLOAT into a STRING and then using VARCHAR2 or a NULL-terminated string for the operation.

STRING

The NULL-terminated STRING format behaves like the VARCHAR2 format, except that the string must contain a NULL terminator character.

Input

The string length supplied in the OCIBindByName() or OCIBindByPos() call limits the scan for the NULL terminator. If the NULL terminator is not found within the length specified, Oracle Database issues the following error:

ORA-01480: trailing NULL missing from STR bind value

If the length is not specified in the bind call, OCI uses an implied maximum string length of 4000.

The minimum string length is 2 bytes. If the first character is a NULL terminator and the length is specified as 2, a NULL is inserted into the column, if permitted. Unlike types VARCHAR2 and CHAR, a string containing all blanks is not treated as a NULL on input; it is inserted as is.

Note:

You cannot pass -1 for the string length parameter of a NULL-terminated string

Output

A NULL terminator is placed after the last character returned. If the string exceeds the field length specified, it is truncated and the last character position of the output variable contains the NULL terminator.

A NULL select-list item returns a NULL terminator character in the first character position. An ORA-01405 error is also possible.

VARNUM

The VARNUM data type is like the external NUMBER data type, except that the first byte contains the length of the number representation. This length does not include the length byte itself. Reserve 22 bytes to receive the longest possible VARNUM. Set the length byte when you send a VARNUM value to Oracle Database.

Table 3-3 shows several examples of the VARNUM values returned for numbers in a table.

Table 3-3 VARNUM Examples

Decimal Value

Length Byte

Exponent Byte

Mantissa Bytes

Terminator Byte

0

1

128

Not applicable

Not applicable

5

2

193

6

Not applicable

-5

3

62

96

102

2767

3

194

28, 68

Not applicable

-2767

4

61

74, 34

102

100000

2

195

11

Not applicable

1234567

5

196

2, 24, 46, 68

Not applicable

LONG

The LONG data type stores character strings longer than 4000 bytes. You can store up to 2 gigabytes (2^31-1 bytes) in a LONG column. Columns of this type are used only for storage and retrieval of long strings. They cannot be used in functions, expressions, or WHERE clauses. LONG column values are generally converted to and from character strings.

Do not create tables with LONG columns. Use LOB columns (CLOB, NCLOB, or BLOB) instead. LONG columns are supported only for backward compatibility.

Oracle also recommends that you convert existing LONG columns to LOB columns. LOB columns are subject to far fewer restrictions than LONG columns. Furthermore, LOB functionality is enhanced in every release, but LONG functionality has been static for several releases.

VARCHAR

The VARCHAR data type stores character strings of varying length. The first 2 bytes contain the length of the character string, and the remaining bytes contain the string. The specified length of the string in a bind or a define call must include the two length bytes, so the largest VARCHAR string that can be received or sent is 65533 bytes long, not 65535.

DATE

The DATE data type can update, insert, or retrieve a date value using the Oracle internal date binary format.

The century and year bytes (bytes 1 and 2) are in excess-100 notation. The first byte stores the value of the year, which is 1992, as an integer, divided by 100, giving 119 in excess-100 notation. The second byte stores year modulo 100, giving 192. Dates Before Common Era (BCE) are less than 100. The era begins on 01-JAN-4712 BCE, which is Julian day 1. For this date, the century byte is 53, and the year byte is 88. The hour, minute, and second bytes are in excess-1 notation. The hour byte ranges from 1 to 24, the minute and second bytes from 1 to 60. If no time was specified when the date was created, the time defaults to midnight (1, 1, 1).

When you enter a date in binary format using the DATE external data type, the database does not do consistency or range checking. All data in this format must be carefully validated before input.

Note:

There is little need to use the Oracle external DATE data type in ordinary database operations. It is much more convenient to convert DATE into character format, because the program usually deals with data in a character format, such as DD-MON-YY.

When a DATE column is converted to a character string in your program, it is returned using the default format mask for your session, or as specified in the INIT.ORA file.

If you are using objects in an Oracle database, you can work with a special OCIDate data type using a set of predefined OCI functions.

RAW

The RAW data type is used for binary data or byte strings that are not to be interpreted by Oracle Database, for example, to store graphics character sequences. The maximum length of a RAW column is 2000 bytes. If the init.ora parameter max_string_size = standard (default value), the maximum length of a RAW can be 2000 bytes. If the init.ora parameter max_string_size = extended, the maximum length of a RAW can be 32767 bytes.

When RAW data in an Oracle Database table is converted to a character string in a program, the data is represented in hexadecimal character code. Each byte of the RAW data is returned as two characters that indicate the value of the byte, from '00' to 'FF'. To input a character string in your program to a RAW column in an Oracle Database table, you must code the data in the character string using this hexadecimal code.

You can use the piecewise capabilities provided by OCIDefineByPos(), OCIBindByName(), OCIBindByPos(), OCIStmtGetPieceInfo(), and OCIStmtSetPieceInfo() to perform inserts, updates, or fetches involving RAW (or LONGRAW) columns.

If you are using objects in an Oracle database, you can work with a special OCIRaw data type using a set of predefined OCI functions. See "Raw (OCIRaw)" for more information about this data type.

VARRAW

The VARRAW data type is similar to the RAW data type. However, the first 2 bytes contain the length of the data. The specified length of the string in a bind or a define call must include the two length bytes, so the largest VARRAW string that can be received or sent is 65533 bytes, not 65535. For converting longer strings, use the LONGVARRAW external data type.

LONG RAW

The LONGRAW data type is similar to the RAW data type, except that it stores raw data with a length up to 2 gigabytes (2^31-1 bytes).

UNSIGNED

The UNSIGNED data type is used for unsigned binary integers. The size in bytes is system-dependent. The host system architecture determines the order of the bytes in a word. A length specification is required for input and output. If the number being output from Oracle Database is not an integer, the fractional part is discarded, and no error or other indication is returned. If the number to be returned exceeds the capacity of an unsigned integer for the system, Oracle Database returns an "overflow on conversion" error.

LONG VARCHAR

The LONGVARCHAR data type stores data from and into an Oracle Database LONG column. The first 4 bytes of a LONGVARCHAR contain the length of the item. So, the maximum length of a stored item is 2^31-5 bytes.

LONG VARRAW

The LONGVARRAW data type is used to store data from and into an Oracle Database LONGRAW column. The length is contained in the first four bytes. The maximum length is 2^31-5 bytes.

CHAR

The CHAR data type is a string of characters, with a maximum length of 2000.

Input

The entire contents of the buffer (value_sz chars) is passed to the database, including any trailing blanks or NULLs.

If the value_sz parameter is zero, Oracle Database treats the bind variable as a NULL, regardless of its actual content. Of course, a NULL must be allowed for the bind variable value in the SQL statement. If you try to insert a NULL into a column that has a NOTNULL integrity constraint, Oracle Database issues an error and does not insert the row.

Negative values for the value_sz parameter are not allowed for CHARs.

When the Oracle internal (column) data type is NUMBER, input from a character string that contains the character representation of a number is legal. Input character strings are converted to internal numeric format. If the CHAR string contains an illegal conversion character, Oracle Database returns an error and does not insert the value. Number conversion follows the conventions established by globalization support settings for your system. For example, your system might be configured to recognize a comma (,) rather than a period (.) as the decimal point.

Output

Specify the desired length for the return value in the value_sz parameter of the OCIDefineByPos() call. If zero is specified for the length, no data is returned.

If you omit the rlenp parameter of OCIDefineByPos(), returned values are blank padded to the buffer length, and NULLs are returned as a string of blank characters. If rlenp is included, returned values are not blank-padded. Instead, their actual lengths are returned in the rlenp parameter.

To check whether a NULL is returned or character truncation occurs, include an indicator parameter or array of indicator parameters in the OCIDefineByPos() call. An indicator parameter is set to -1 when a NULL is fetched and to the original column length when the returned value is truncated. Otherwise, it is set to zero. If you do not specify an indicator parameter and a NULL is selected, the fetch call returns an ORA-01405 error.

You can also request output to a character string from an internal NUMBER data type. Number conversion follows the conventions established by the globalization support settings for your system. For example, your system might use a comma (,) rather than a period (.) as the decimal point.

CHARZ

The CHARZ external data type is similar to the CHAR data type, except that the string must be NULL-terminated on input, and Oracle Database places a NULL-terminator character at the end of the string on output. The NULL terminator serves only to delimit the string on input or output; it is not part of the data in the table.

On input, the length parameter must indicate the exact length, including the NULL terminator. For example, if an array in C is declared as follows, then the length parameter when you bind my_num must be seven. Any other value would return an error for this example.

char my_num[] = "123.45";

The following new external data types were introduced with or after release 8.0. These data types are not supported when you connect to an Oracle release 7 server.

Note:

Both internal and external data types have Oracle-defined constant values, such as SQLT_NTY, SQLT_REF, corresponding to their data type codes. Although the constants are not listed for all of the types in this chapter, they are used in this section when discussing new Oracle data types. The data type constants are also used in other chapters of this guide when referring to these new types.

Named Data Types: Object, VARRAY, Nested Table

Named data types are user-defined types that are specified with the CREATETYPE command in SQL.

Examples include object types, varrays, and nested tables. In OCI, named data type refers to a host language representation of the type. The SQLT_NTY data type code is used when binding or defining named data types.

In a C application, named data types are represented as C structs. These structs can be generated from types stored in the database by using the Object Type Translator. These types correspond to OCI_TYPECODE_OBJECT.

ROWID Descriptor

In this case, you can use the returned ROWID in further DELETE statements.

If you are performing a SELECT for UPDATE, the ROWID is implicitly returned. This ROWID can be read into a user-allocated ROWID descriptor by using OCIAttrGet() on the statement handle and used in a subsequent UPDATE statement. The prefetch operation fetches all ROWIDs on a SELECT for UPDATE; use prefetching and then a single row fetch.

You access rowids using a ROWID descriptor, which you can use as a bind or define variable.

LOB Descriptor

A LOB (large object) stores binary or character data up to 128 terabytes (TB) in length.

Binary data is stored in a BLOB (binary LOB), and character data is stored in a CLOB (character LOB) or NCLOB (national character LOB).

LOB values may or may not be stored inline with other row data in the database. In either case, LOBs have the full transactional support of the Oracle database. A database table stores a LOB locator that points to the LOB value, which may be in a different storage space.

When an OCI application issues a SQL query that includes a LOB column or attribute in its select list, fetching the results of the query returns the locator, rather than the actual LOB value. In OCI, the LOB locator maps to a variable of type OCILobLocator.

Note:

Depending on your application, you may or may not want to use LOB locators. You can use the data interface for LOBs, which does not require LOB locators. In this interface, you can bind or define character data for CLOB columns or RAW data for BLOB columns.

The OCI functions for LOBs take a LOB locator as one of their arguments. The OCI functions assume that the locator has already been created, whether or not the LOB to which it points contains data.

Bind and define operations are performed on the LOB locator, which is allocated with the OCIDescriptorAlloc() function.

The locator is always fetched first using SQL or OCIObjectPin(), and then operations are performed using the locator. The OCI functions never take the actual LOB value as a parameter.

The data type codes available for binding or defining LOBs are:

SQLT_BLOB - A binary LOB data type

SQLT_CLOB - A character LOB data type

The NCLOB is a special type of CLOB with the following requirements:

To write into or read from an NCLOB, the user must set the character set form (csfrm) parameter to be SQLCS_NCHAR.

The amount (amtp) parameter in calls involving CLOBs and NCLOBs is always interpreted in terms of characters, rather than bytes, for fixed-width character sets.

BFILE

Oracle Database supports access to binary files (BFILEs).

The BFILE data type provides access to LOBs that are stored in file systems outside an Oracle database.

A BFILE column or attribute stores a file LOB locator, which serves as a pointer to a binary file on the server's file system. The locator maintains the directory object and the file name. The maximum size of a BFILE is the smaller of the operating system maximum file size or UB8MAXVAL.

Binary file LOBs do not participate in transactions. Rather, the underlying operating system provides file integrity and durability.

The database administrator must ensure that the file exists and that Oracle Database processes have operating system read permissions on the file.

BLOB

The BLOB data type stores unstructured binary large objects. BLOBs can be thought of as bit streams with no character set semantics. BLOBs can store up to 128 terabytes of binary data.

BLOBs have full transactional support; changes made through OCI participate fully in the transaction. The BLOB value manipulations can be committed or rolled back. You cannot save a BLOB locator in a variable in one transaction and then use it in another transaction or session.

CLOB

The CLOB data type stores fixed-width or variable-width character data. CLOBs can store up to 128 terabytes of character data.

CLOBs have full transactional support; changes made through OCI participate fully in the transaction. The CLOB value manipulations can be committed or rolled back. You cannot save a CLOB locator in a variable in one transaction and then use it in another transaction or session.

NCLOB

An NCLOB is a national character version of a CLOB. It stores fixed-width, single-byte or multibyte national character set (NCHAR) data, or variable-width character set data. NCLOBs can store up to 128 terabytes of character text data.

NCLOBs have full transactional support; changes made through OCI participate fully in the transaction. NCLOB value manipulations can be committed or rolled back. You cannot save an NCLOB locator in a variable in one transaction and then use it in another transaction or session.

ANSI DATE

ANSIDATE is based on DATE, but contains no time portion. It also has no time zone. ANSIDATE follows the ANSI specification for the DATE data type. When assigning an ANSIDATE to a DATE or a time stamp data type, the time portion of the Oracle DATE and the time stamp are set to zero. When assigning a DATE or a time stamp to an ANSIDATE, the time portion is ignored.

Instead of using the ANSI DATE data type, Oracle recommends that you use the TIMESTAMP data type, which contains both date and time.

TIMESTAMP

The TIMESTAMP data type is an extension of the DATE data type. It stores the year, month, and day of the DATE data type, plus the hour, minute, and second values. It has no time zone. The TIMESTAMP data type has the following form:

TIMESTAMP(fractional_seconds_precision)

In this form, the optional fractional_seconds_precision specifies the number of digits in the fractional part of the SECOND datetime field and can be a number in the range 0 to 9. The default is 6.

TIMESTAMP WITH TIME ZONE

TIMESTAMPWITHTIMEZONE (TSTZ) is a variant of TIMESTAMP that includes an explicit time zone displacement in its value. The time zone displacement is the difference in hours and minutes between local time and UTC (coordinated universal time—formerly Greenwich mean time). The TIMESTAMPWITHTIMEZONE data type has the following form:

TIMESTAMP(fractional_seconds_precision) WITH TIME ZONE

In this form, fractional_seconds_precision optionally specifies the number of digits in the fractional part of the SECOND datetime field, and can be a number in the range 0 to 9. The default is 6.

Two TIMESTAMPWITHTIMEZONE values are considered identical if they represent the same instant in UTC, regardless of the TIMEZONE offsets stored in the data.

TIMESTAMP WITH LOCAL TIME ZONE

TIMESTAMPWITHLOCALTIMEZONE (TSLTZ) is another variant of TIMESTAMP that includes a time zone displacement in its value. Storage is in the same format as for TIMESTAMP. This type differs from TIMESTAMPWITHTIMEZONE in that data stored in the database is normalized to the database time zone, and the time zone displacement is not stored as part of the column data. When retrieving the data, Oracle Database returns it in your local session time zone.

The time zone displacement is the difference (in hours and minutes) between local time and UTC (coordinated universal time—formerly Greenwich mean time). The TIMESTAMPWITHLOCALTIMEZONE data type has the following form:

TIMESTAMP(fractional_seconds_precision) WITH LOCAL TIME ZONE

In this form, fractional_seconds_precision optionally specifies the number of digits in the fractional part of the SECOND datetime field and can be a number in the range 0 to 9. The default is 6.

INTERVAL YEAR TO MONTH

INTERVALYEARTOMONTH stores a period of time using the YEAR and MONTH datetime fields. The INTERVALYEARTOMONTH data type has the following form:

INTERVAL YEAR(year_precision) TO MONTH

In this form, the optional year_precision is the number of digits in the YEAR datetime field. The default value of year_precision is 2.

INTERVAL DAY TO SECOND

INTERVALDAYTOSECOND stores a period of time in terms of days, hours, minutes, and seconds. The INTERVALDAYTOSECOND data type has the following form:

INTERVAL DAY (day_precision) TO SECOND(fractional_seconds_precision)

In this form:

day_precision is the number of digits in the DAY datetime field. It is optional. Accepted values are 0 to 9. The default is 2.

fractional_seconds_precision is the number of digits in the fractional part of the SECOND datetime field. Accepted values are 0 to 9. The value should be provided as nanoseconds. The Default Day to Second precision is 6 unless the precision is specified to a different value at the time of creating the table. In this case, the least significant three digits will be truncated.

About Avoiding Unexpected Results Using Datetime

Note:

To avoid unexpected results in your data manipulation language (DML) operations on datetime data, you can verify the database and session time zones by querying the built-in SQL functions DBTIMEZONE and SESSIONTIMEZONE. If the time zones have not been set manually, Oracle Database uses the operating system time zone by default. If the operating system time zone is not a valid Oracle Database time zone, Oracle Database uses UTC as the default value.

Native Float and Native Double

The native float (SQLT_BFLOAT) and native double (SQLT_BDOUBLE) data types represent the single-precision and double-precision floating-point values. They are represented natively, that is, in the host system's floating-point format.

These external types were added in release 10.1 to externally represent the BINARY_FLOAT and BINARY_DOUBLE internal data types. Thus, performance for the internal types is best when used in conjunction with external types native float and native double respectively. This draws a clear distinction between the existing representation of floating-point values (SQLT_FLT) and these types.

Data Conversions for Datetime and Interval Data Types

Shows the data conversion for datetime and interval data types.

You can also use one of the character data types for the host variable used in a fetch or insert operation from or to a datetime or interval column. Oracle Database does the conversion between the character data type and datetime or interval data type for you (see Table 3-7.

Assignment Notes

When you assign a source with a time zone to a target without a time zone, the time zone portion of the source is ignored. When you assign a source without a time zone to a target with a time zone, the time zone of the target is set to the session's default time zone.

When you assign an Oracle Database DATE to a TIMESTAMP, the TIME portion of the DATE is copied over to the TIMESTAMP. When you assign a TIMESTAMP to Oracle Database DATE, the TIME portion of the result DATE is set to zero. This is done to encourage upgrading of Oracle Database DATE to ANSI-compliant DATETIME data types.

When you assign an ANSIDATE to an Oracle DATE or a TIMESTAMP, the TIME portion of the Oracle Database DATE and the TIMESTAMP are set to zero. When you assign an Oracle Database DATE or a TIMESTAMP to an ANSI DATE, the TIME portion is ignored.

When you assign a DATETIME to a character string, the DATETIME is converted using the session's default DATETIME format. When you assign a character string to a DATETIME, the string must contain a valid DATETIME value based on the session's default DATETIME format

When you assign a character string to an INTERVAL, the character string must be a valid INTERVAL character format.

Data Conversion Notes for Datetime and Interval Types

When you convert from TSLTZ to CHAR, DATE, TIMESTAMP, and TSTZ, the value is adjusted to the session time zone.

When you convert from CHAR, DATE, and TIMESTAMP to TSLTZ, the session time zone is stored in memory.

When you assign TSLTZ to ANSIDATE, the time portion is zero.

When you convert from TSTZ, the time zone that the time stamp is in is stored in memory.

When you assign a character string to an interval, the character string must be a valid interval character format.

Datetime and Date Upgrading Rules

OCI has full forward and backward compatibility between a client application and the Oracle database for datetime and date columns.

Pre-9.0 Client with 9.0 or Later Server

The only datetime data type available to a pre-9.0 application is the DATE data type, SQLT_DAT. When a pre-9.0 client that defined a buffer as SQLT_DAT tries to obtain data from a TSLTZ column, only the date portion of the value is returned to the client.

Pre-9.0 Server with 9.0 or Later Client

When a pre-9.0 server is used with a 9.0 or later client, the client can have a bind or define buffer of type SQLT_TIMESTAMP_LTZ. The following compatibilities are maintained in this case.

If any client application tries to insert a SQLT_TIMESTAMP_LTZ (or any of the new datetime data types) into a DATE column, an error is issued because there is potential data loss in this situation.

When a client has an OUT bind or a define buffer that is of data type SQLT_TIMESTAMP_LTZ and the underlying server-side SQL buffer or column is of DATE type, then the session time zone is assigned.

Data Conversion for BINARY_FLOAT and BINARY_DOUBLE in OCI

Table 3-8 shows the supported conversions between internal numeric data types and all relevant external types. An (I) implies that the conversion is valid for input only (binds), and (O) implies that the conversion is valid for output only (defines). An (I/O) implies that the conversion is valid for input and output (binds and defines).

An (I/O) implies that the conversion is valid for input and output (binds and defines)

Table 3-9 shows the supported conversions between all relevant internal types and numeric external types. An (I) implies that the conversion is valid for input only (only for binds), and (O) implies that the conversion is valid for output only (only for defines). An (I/O) implies that the conversion is valid for input and output (binds and defines).

Typecodes

This typecode identifies the type, and is used by Oracle Database to manage information about object type attributes. This typecode system is designed to be generic and extensible. It is not tied to a direct one-to-one mapping to Oracle data types. Consider the following SQL statements:

These statements create an object type and an object table. When it is created, my_table has three columns, all of which are of Oracle NUMBER type, because SMALLINT and INTEGER map internally to NUMBER. The internal representation of the attributes of my_type, however, maintains the distinction between the data types of the three attributes: attr1 is OCI_TYPECODE_NUMBER, attr2 is OCI_TYPECODE_INTEGER, and attr3 is OCI_TYPECODE_SMALLINT. If an application describes my_type, these typecodes are returned.

OCITypeCode is the C data type of the typecode. The typecode is used by some OCI functions, like OCIObjectNew(), where it helps determine what type of object is created. It is also returned as the value of some attributes when an object is described; for example, querying the OCI_ATTR_TYPECODE attribute of a type returns an OCITypeCode value.

Table 3-10 lists the possible values for an OCITypeCode. There is a value corresponding to each Oracle data type.

Relationship Between SQLT and OCI_TYPECODE Values

Oracle Database recognizes two different sets of data type code values. One set is distinguished by the SQLT_ prefix, the other by the OCI_TYPECODE_ prefix.

The SQLT typecodes are used by OCI to specify a data type in a bind or define operation, enabling you to control data conversions between Oracle Database and OCI client applications. The OCI_TYPECODE types are used by Oracle's type system to reference or describe predefined types when manipulating or creating user-defined types.

In many cases, there are direct mappings between SQLT and OCI_TYPECODE values. In other cases, however, there is not a direct one-to-one mapping. For example, OCI_TYPECODE_SIGNED8, OCI_TYPECODE_SIGNED16, OCI_TYPECODE_SIGNED32, OCI_TYPECODE_INTEGER, OCI_TYPECODE_OCTET, and OCI_TYPECODE_SMALLINT are all mapped to the SQLT_INT type.

Table 3-11 illustrates the mappings between SQLT and OCI_TYPECODE types.

These are floating-point numbers, the precision is given in terms of binary digits. b is the precision of the number in binary digits.

Footnote 25

This is equivalent to a NUMBER with no decimal places.

Footnote 26

i is the size of the number in bytes, set as part of an OCI call.

Footnote 27

p is the precision of the number in decimal digits; s is the scale of the number in decimal digits.

Footnote 28

Can only be part of a named collection type.

Definitions in oratypes.h

Throughout this guide there are references to data types like ub2 or sb4, or to constants like UB4MAXVAL. These types are defined in the oratypes.h header file, which is found in the public directory. The exact contents may vary according to the operating system that you are using.

Note:

The use of the data types in oratypes.h is the only supported means of supplying parameters to OCI.